Successful
use of DWT requires a well-formed geometry model without problems of wake
misbehavior, leakage, panel disproportion, and so on. Regions of the model
surface corresponding to control surfaces must have been defined as tilt
panels. If nonlinear analyses are to be used, the model must be free of
large areas of separated flow and discontinuous streamlines.

The first
step in running DWT is to fill in an opening form with some basic geometry
information about the model. Some items can be omitted; for example, moments
of inertia are not required if the dynamic stability evaluation is omitted.

Next comes
a second form specific to the type of analysis to be run. Five categories
of analysis are provided.

Pitch
and Yaw Stability

The basic
procedure is to define ranges of angle of attack or sideslip and elevator
or rudder deflection. For linear analyses, only two angles and deflections
are required; nonlinear analyses call more repetitions. The design point
- equilibrium for a given attitude and CG location - is extrapolated from
the results.

Roll rate

Roll rate
is calculated using a combination of direct Cmarc analysis and an empirically-based
adjustment.

Sensitivity

The Sensitivity
analysis displays the degree to which six stability coefficients are influenced
by five variables, including time stepping parameters.

Many methods
have historically been used to obtain stability derivatives, including
flight test, wind tunnel investigation, and various numerical procedures,
many of which are epitomized by the so-called DATCOM. Results from Digital
Wind Tunnel fall within the normal bounds of variation among methods.